The present invention relates to the electronics arts. It particularly relates to an electronic module for automotive applications as well as to a receiving element with an integrated electronic module therein, and will be described with particular reference thereto. However, the invention also finds application in electronic modules of other types and for other uses.
It is known to check for proper locking in an automotive seat belt restraining system by means of a terminal switch disposed inside the lock. The switch detects when the belt locking element is inserted into the lock. The terminal switch thus monitors whether the seated person has closed the belt correctly. In the event the lock is incorrectly engaged, an alarm or other warning signal can be generated.
Recently, however, there has been a demand in the automotive industry for improved vehicle safety. This demand has generated a desire to recognize malfunctions of the device that monitors the locking of the seat belt lock. In particular, such monitoring is desirable when the locking information is used for selectively controlling the activation of one or more airbags. For example, it is possible to selectively control the chronological order of airbag activation. It is also possible to control airbag activation with respect to degree of fullness or its filling velocity, depending upon whether or not the person being protected thereby is buckled down.
The monitoring device therefor typically requires the utilization of appropriate electronics.
The installation of such electronics in a seat belt buckle of a car seat belt system, however, poses certain difficulties. The electronics must be integrated into the seat belt buckle typically within an extremely limited space. At the same time, the electronics inside the seat belt buckle must be adequately protected from vibrations, mechanical shocks, and other environmental influences which typically occur in a motor vehicle.
In accordance with the invention, an electronic module is provided which, given positive and non-positive integration, is adequately protected from vibrations and mechanical shocks as well as other environmental influences. The electronic module is preferably manufacturable at a low cost. In another embodiment, the electronic module is integrated into a receiving element, in particular a belt buckle for a seat belt, which satisfies the aforementioned requirements.
By invention-specific enveloping of the electrical circuit-board conductors and the electronic and electromechanical components within a plastic material having low Shore Hardness, an elastic casing is produced which protects the electronic module from environmental influences. This overall structure combines, as desired, the electronic components and circuit board conductors into a single module. Furthermore, by using the soft plastic casing with positive or non-positive integration of the electronic module into a receiving element, vibrations and mechanical shocks are transmitted only in an attenuated manner to the circuit board conductors, the components, and particularly to the connection sites where the components connect with the circuit board conductors. The module is thus adequately protected from mechanical damage.
The circuit board conductors and components are encased within a relatively soft plastic material which preferably has a Shore Hardness of less than or equal to 60, preferably between 25 and 60 Shore, and most preferably between 40 and 60 Shore. This enables spray-encasement of the circuit board conductors and components in a relatively simple and cost-effective manner.
The components can be arranged, for example, on a stamped grid, a printed circuit board or any other form of circuit board as desired. In the event that a stamped grid is employed, the encasement with the relatively soft plastic material simultaneously provides adequate fixing of the circuit board conductors and components. Modules formed this way are mechanically unstable or flexible overall, but fully electrically functional.
The plastic encasement is formed in such a fashion that at least portions of the plastic are shaped for simple positive and/or non-positive connection with a receiving element. For example, the plastic encasement is selectively provided with suitable projections by means of which the module is securely retained in the receiving element.
According to one embodiment of the invention, the relatively soft plastic sheathing is encased, at least partially, within a covering of rigid plastic, preferably using a spray-encasing process. This provides mechanical stabilization, particularly when the circuit board conductors are formed as a stamped grid. In particular, this arrangement enables simple installation of the module in a receiving element, for example via snap-in connections, welding, e.g. ultra-sound welding, screw-fastening, or the like.
In another embodiment of the invention, the receiving element having the electronic module integrated therein is injecting or poured with its relatively soft plastic covering into a receiving element. This results, just as with installation of a module having an additional hard plastic casing, in a flexible or resilient bedding of the electronic module in the receiving element.
In an additional embodiment, the electronic module with its circuit board connectors or printed circuit board are fixed directly into the receiving element at one or several locations as desired. Preferably, the circuit board connectors or printed circuit board are not connected to the receiving element to the extent that the circuit board conductors overall are rigidly retained in the module. Additionally, this arrangement provides adequate resilient and/or vibration-attenuating bedding of the essential components of the electronics, in particular the electronic components of the electronic module.